Method for monitoring the boron content of borophosphosilicate

Abstract

A method for monitoring the boron content of the borophosphosilicate, BPSG. The BPSG is obtained by the oxidation of silane, of diborane and of phosphine in a reactor, starting with a first, diborane/silane gas mixture and a second, phosphine/silane gas mixture by monitoring the ratio ρ=diborane/(diborane+silane) of the mixture resulting from the mixing of the first and second gas mixtures. Monitoring of the boron content is obtained by measuring the density of the first mixture, determining the amount of residual hydrogen in the first mixture and modulating the mass flow rate of the first mixture in response to the calculated ratio ρ.

I claim: 
     
       1. A method for monitoring the boron content of the borophosphosilicate obtained by oxidation of silane, of diborane and of phosphine in a reactor, starting with a first, diborane/silane gas mixture and a second, phosphine/silane gas mixture by monitoring the ratio ρ=diborane/(diborane+silane) of the mixture resulting from the mixing of the first and second gas mixtures, wherein said method comprises: measuring the density of said first mixture,   determining the amount of residual hydrogen H 2  in said first mixture from the measured density,   calculating the ratio ρ=diborane/(diborane+silane) using the determined amount of residual H 2 ,   modulating the mass flow rate of said first mixture, in response to the calculated ratio ρ, to regulate the boron content of the borophosphosilicate.   
     
     
       2. The method according to claim 1, wherein said first mixture comprises of G% of diborane and (100-G) % of silane, said second mixture having G% of phosphine and (100-G) % of silane, the amount of hydrogen measured in said first mixture having a value X, the ratio ρ=diborane/(diborane+silane) satisfying the equation:   ρ=[(G/100-X)·A]/[(G/100-X)·A+E+(100-G)/100(A+D)]     wherein the following components are defined:   G designates the percentage of diborane in the first mixture   A designates the flow-rate of the first mixture   D designates the flow-rate of the second mixture   E designates the flow-rate of the silane   X designates the amount of residual hydrogen in the first mixture.